The present invention relates to a system and a method for improving performance of an exhaust gas after-treatment system, and more particularly to regenerating a catalyst to improve its NOx conversion efficiency.
Current emission control regulations necessitate the use of catalysts in the exhaust systems of automotive vehicles in order to convert carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) produced during engine operation into harmless exhaust gasses. Vehicles equipped with diesel or lean gasoline engines offer the benefit of increased fuel economy. Such vehicles can benefit from exhaust after-treatment systems that employ one or more catalysts to assist in chemically converting NOx, hydrocarbons, carbon monoxide, and other pollutants into less harmful compounds prior to discharge of the exhaust to the environment.
However, in such traditional catalyst systems, soot, hydrocarbons, and other undesirable species may adsorb on the surface of the catalyst, thus contaminating the catalyst and reducing its conversion efficiency. Periodically heating the catalyst systems to a temperature above the boiling point of hydrocarbons, or the regeneration temperature of soot, for a predetermined amount of time, can regenerate the catalyst by removing deposits of undesirable materials.
Known methods of regeneration may involve complex operations such as switching many streams of exhaust and activating many valves. Such systems employ complex subsystems such as cooling fans, multiple catalyst beds, and the like. Additionally, these systems also require valuable space, materials and additional fuel consumption. Therefore, there is need for an improved system and method for regeneration of catalysts.